The present invention relates to switching regulators and more particularly to a soft start circuit for such regulators.
Electronic apparatus such as supervisory control circuits for two valve-type micropumps, as disclosed, for example, in U.S. patent application Ser. No. 07/599,298 in the name of Hajime Miyazaki et al., filed Oct. 17, 1990, the disclosure of which is hereby incorporated by reference, are capable of exercising precise flow control in trace amounts. Therefore, such valves and control circuits are particularly suited for medical care applications, such as the administration of insulin to diabetics, and chemical analysis. Where such control circuits, or micropumps, are intended for medical applications, safety and reliability present important problems. Frequency control and regulation in current control systems for such sensitive applications have proven to be less accurate or reliable than desired. It has proven difficult to maintain adequate frequency regulation during initial power up when power supply voltages have not yet stabilized under a sudden load. The selection and control over start up frequency is typically too variable and prone to error. Therefore, what is needed is a new method and apparatus for providing adequate switching regulation for such control circuits.